Embossing is a well-known technique to permanently mark plastic cards, such as credit cards, with alphanumerical characters and other symbols. It is typically applied at the end of the card production process, which includes laminating, under pressure and at high temperature, one or more layers of plastic onto a core sheet molded from an appropriate material such as the plastic resin polyvinyl chloride acetate (PVCA). One such process is disclosed in great detail in U.S. Pat. No. 4,100,011 [U.S. Pat. No. 4,100,011 B (FOOTE) 1978, Jul. 11].
The embossed text appearing on credit cards can be used to mechanically transfer the relevant card information onto a piece of carbon paper. Before the advent of electronic information carriers such as magnetized stripes and embedded integrated circuits on credit cards, the mechanical reproduction of embossed text on carbon paper and subsequent signing of the paper was the most common way to carry out credit card transactions. Although only a minority of today's credit card transactions still rely on the embossed text, embossing is still perceived by some as a security feature, as it adds a degree of difficulty to the process of counterfeiting credit cards.
Embossing is a mechanical process in which a “male” stamp of a character is punched into the rear side of the plastic card, while a “female” die is pushed against the front side. Machines for high-speed and high-precision embossing of plastic cards are known in the art, such as the one disclosed by LaManna et al. in U.S. Pat. No. 4,686,898 [U.S. Pat. No. 4,686,898 B (LAMANNA ET AL.) 1987, Aug. 18].
Embossing causes local permanent deformation of the material out of which the card is produced. Plastics are very amenable to this purpose. Modern credit cards or credit card sized devices, however, may include the functions of a contactless chip card or an authentication token, implemented by means of electronic components and wiring which would be damaged if subjected to the embossing process.
For example, the sensitivity of the wiring making up the antenna of a contactless smart card is recognized in the art, a fact that has prompted inventions such as those disclosed in [US 20010030238 A (ARISAWA) 2001, Oct. 18], [US 20080277484 A (LAUNAY ET AL.) 2008, Nov. 13], [US 20080203171 A (PHILIPS) 2008, Aug. 28], and [US 20070267506 A (BASHAN ET AL.) 2007, Nov. 22], which rely on avoiding overlap between the antenna wiring and the reserved embossing area.
More generally, the electronic devices to which the present invention applies comprise a processing device for carrying out an action, a button for initiating said action, and the necessary interconnection between these elements.
In this application, “slim electronic devices” or “slim electronic apparatus” refers to devices or apparatus with a thickness similar to that of a credit card. In this application, “credit card size” refers to the standardized size of ID-1 cards according to ISO/IEC standard 7810. Additional specifications for the size and finishing of such cards can be found in ISO/IEC standards 7811 and 7813.
By adding appropriate elements such as an agent for generating client credentials and a display, a credit card sized authentication token can be obtained. The function of an authentication token is to electronically generate authentication credentials, also known as one-time passwords, by cryptographically combining a key with at least one of a counter value, a time value, or data entered by the user.
In order to perform authentication, it is essential that the central authentication infrastructure disposes of an equivalent copy of the counter, the time value, or the entered data. Depending on the details of the cryptographic functions used, the central authentication infrastructure either uses this copy to generate a local instance of the client credential for comparison with the received client credential, or it extracts the value of the variable from the received client credential and compares that value with the central copy.